linux-kernel - Re: [RFC PATCH] page_alloc: allow migration of smaller hugepages during contig

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Message-ID: <57b5ee51-db68-4106-9e3c-cb2518457e5d@redhat.com>
Date: Mon, 20 Oct 2025 22:38:27 +0200
From: David Hildenbrand <david@...hat.com>
To: Gregory Price <gourry@...rry.net>
Cc: Zi Yan <ziy@...dia.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, kernel-team@...a.com,
 akpm@...ux-foundation.org, vbabka@...e.cz, surenb@...gle.com,
 mhocko@...e.com, jackmanb@...gle.com, hannes@...xchg.org
Subject: Re: [RFC PATCH] page_alloc: allow migration of smaller hugepages
 during contig_alloc.

On 20.10.25 22:27, Gregory Price wrote:
> On Mon, Oct 20, 2025 at 10:17:42PM +0200, David Hildenbrand wrote:
>> Yes, it's completely racy.
>>
>> I was primarily concerned about us calling functions that will VM_WARN_ON()
>> etc due to the races; not that they would make us accept/jump over a range
>> although we shouldn't.
>>
>> Of course, regarding the latter, we want to try as good as possible to avoid
>> jumping over ranges that we can actually handle.
>>
> 
> I'll go ahead and add a snapshot_page.

I'd say it's probably good enough initially to just use compound_head() 
and filter out crazy values.

-- 
Cheers

David / dhildenb